How to add the rows in a for loop

I have the following code,

labels = 1:100;
element_positions = zeros(length(labels-10),4)
for i = [1:9,11:19,21:29,31:39,41:49,51:59,61:69,71:79,81:89];
element_positions = [nodes(i,:),nodes(i+1,:);
                         nodes(i,:),nodes(i+10,:);
                         nodes(i,:),nodes(i+11,:);
                         nodes(i+10,:),nodes(i+1,:)]
end

I want to make an element matrix in which I couple the nodes to a full matrix, instead of computing 9 indepentendt matrices, how do i make a for loop that adds them?

I already tried

labels = 1:100;
element_positions = zeros(length(labels-10),4)
for i = [1:9,11:19,21:29,31:39,41:49,51:59,61:69,71:79,81:89];
element_positions(i,:) = [nodes(i,:),nodes(i+1,:);
                         nodes(i,:),nodes(i+10,:);
                         nodes(i,:),nodes(i+11,:);
                         nodes(i+10,:),nodes(i+1,:)]
end

but then it get the errror: Unable to perform assignment because the size of the left side is 1-by-4 and the size of the right side is 4-by-4.

Thanks in advance,

Frank

[Luna]

What is the nodes?

[Frank Oosterveld]

nodes is a 100 x 2 double matrix

m = n = 9
xpos = [0:n 0:n 0:n 0:n 0:n 0:n 0:n 0:n 0:n 0:n]'; 
ypos = reshape( repmat( [0:n], m+1,1 ), 1, [] )';
nodes = [xpos, ypos];

Answer 1

[KSSV]

Should be something like this to solve error.

labels = 1:100;
element_positions = zeros(length(labels-10),4)
for i = [1:9,11:19,21:29,31:39,41:49,51:59,61:69,71:79,81:89];
element_positions(i,:) = [nodes(i,1),nodes(i+1,2);
                         nodes(i,2),nodes(i+10,3);
                         nodes(i,3),nodes(i+11,4);
                         nodes(i+10,4),nodes(i+1,1)]
end

[Frank Oosterveld]

This doesn't work since the nodes matrix has only 2 columns.

I want to end up with a matrix of 4 columns and 100 rows.

[KSSV]

What is your domain? What FEM element you are using?

[Frank Oosterveld]

This is what i eventually want to make, therefore I need the connection_matrix, which I try to obtain by the proposed for-loop.

Answer 2

[madhan ravi]

labels = 1:100;
element_positions = cell(1,length(labels-10));  %preallocation
ctr=1;
for i = [1:9,11:19,21:29,31:39,41:49,51:59,61:69,71:79,81:89];
element_positions{ctr} = [nodes(i,1),nodes(i+1,2);
                         nodes(i,2),nodes(i+10,3);
                         nodes(i,3),nodes(i+11,4);
                         nodes(i+10,4),nodes(i+1,1)]
ctr=ctr+1;
end
celldisp(element_positions)
[element_positions{:}]  %double matrix

[Frank Oosterveld]

Thanks for your fast answer,

Only thing is that this exceeds my node matrix. I want to end up with a matrix with 4 columns, starting from a input matrix of 2 columns, then i want to end up with a matrix as;

for i = 1

[xpos_node1, ypos_node1, xpos_node2, ypos_node2;

xpos_node1,ypos_node1, xpos_node_11, ypos_node 11;

xpos_node1, ypos_node1, xpos_node_12, ypos_node_12;

xpos_node11, ypos_node11, xpos_node_2, ypos_node_2]

etcetera.

[madhan ravi]

what’s the size of your matrix when you try my answer?

[Frank Oosterveld]

It won't work since you are asking the 3th and 4th columnelement of a matrix with 2 columns